1. Field of the Invention
The invention relates to a digital to time converter, and more particularly to a digital to time converter with high resolution and linearity.
2. Description of the Related Art
In the recent years, Automatic Test Equipments (ATEs) have been generally used as a measurement instrument for measuring the operation timing of Integrated Circuits (ICs). Compared with manual measurement, ATEs test ICs more efficiently and accurately. Among them, the built-in self-test (BIST) becomes the main stream of ATEs due to its low cost. A digital input front-end is the most important module of ATEs. A major component of the digital input front-end module is the Digital-to-Time Converter, or so-called Digital Pulse Generator, which generates a timing signal with a width proportional to the value of a digital control words. The timing signal is passed to the device under test (DUT) through a test channel and the measurement results are further compared to the results pre-stored in the internal memory of the ATE to determine whether the DUT is able to function properly within the predetermined timing delay and whether the output of the DUT is as expected.
However, the performance of conventional digital-to-time converters is easily affected by process, voltage and temperature (PVT) variations. Thus, the linearity of conventional digital-to-time converters is poor, and the corresponding accuracy is not satisfactory. Based on high speed and high resolution requirements, some digital-to-time converters are improved to achieve high performance conversion ate the expense of high power consumption, large chip area and high fabrication cost. Thus, a novel digital-to-time converter with low fabrication costs high resolution, high linearity, low power consumption and low sensitivity to PVT variations is needed.